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                [Usaco2010 Nov]Buying Feed 购买饲料                </h1>
                <p>时间限制：20s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：64MB</p>			</div>
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                                <h3>题目描述</h3><p><div><span style="font-size: medium">&nbsp;&nbsp;约翰开车来到镇上，他要带K吨饲料回家。运送饲料是需要花钱的，如果他的车上有X吨饲料，每公里就要花费X^2元，开车D公里就需要D* X^2元。约翰可以从N家商店购买饲料，所有商店都在一个坐标轴上，第i家店的位置是Xi，饲料的售价为每吨Ci元，库存为Fi。</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;约翰从坐标X=O开始沿坐标轴正方向前进，他家在坐标X=E上。为了带K吨饲料回家，</span></div>
<div><span style="font-size: medium">约翰最少的花费是多少呢？假设所有商店的库存之和不会少于K。</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;举个例子，假设有三家商店，情况如下所示：</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;坐标&nbsp;&nbsp;&nbsp;&nbsp;X=1&nbsp;&nbsp;&nbsp;&nbsp;X=3&nbsp;&nbsp;&nbsp;&nbsp;X=4&nbsp;&nbsp;&nbsp;&nbsp;E=5</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;库存&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;售价&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2</span></div>
<div><span style="font-size: medium">&nbsp;&nbsp;&nbsp;&nbsp;如果K=2，约翰的最优选择是在离家较近的两家商店购买饲料，则花在路上的钱是</span><span style="font-size: medium">1+4=5，花在商店的钱是2+2=4，共需要9元。</span></div></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium">第1行:三个整数K,E,N 第2..N+1行:第i+1行的三个整数代表,X_i,F_i,C_i. </span></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium">一个整数,代表最小花费 </span></p></p><hr/><h3>样例输入</h3><pre>2 5 3
3 1 2
4 1 2
1 1 1

</pre><hr/><h3>样例输出</h3><pre>9</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>Gold</p>
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